Rectilinear acoustical transducer inspection apparatus

ABSTRACT

A rectilinear acoustical transducer and inspection apparatus for use as a non-destructive testing device, whereby workpieces such as structural stiffeners relating to aircraft and the like are inspected for defects or flaws. The apparatus comprises a carriage having rollers mounted therein for direct vehicular contact with the rib portion of the workpiece, whereby the carriage can transverse rectilinearly thereon and including an acoustical transducer pivotably mounted to the carriage having a locomotive means attached thereto by which the transducer is oscillated about its pivot point effecting a walking action to be imparted along the rib, thereby providing the necessary rectilinear motion throughout the length of the rib for the total rapid inspection of the workpiece. The transducer is adapted to removably receive a dry adhesive couplant, which forms a driving mechanical bond and acoustical couple between the piezoelectrical element of the transducer and the workpiece surface.

Miller X Z Q [45] Feb. 5, 1974 1 RECTILINEAR ACOUSTICAL [57 ABSTRACT511/ TRANSDUCER INSPECTION APPARATUS A ,1 l d d recti lnear acousticatrans ucer an inspection ap- [75] Inventor g fi Miller Los Angelesparatus for use as a non-destructive testing device,

a l whereby workpieces such as structural stiffeners relat- [73]Assignee: North American Rockwell ing to aircraft and the like areinspected for defects or Corporation, El S d C lif, flaws. The apparatuscomprises a carriage haying r ql;

. lers mounted therein for direct vehicular contact with [22] Flled:July 1972 ti nb portion of the workpiece, whereby the carriage [2i]Appl. No.: 269,660 can transverse rectilinearly thereon and including anacoustical transduce r p ivgtab ly mounted to the carriage having alocomotive means attached thereto by vThich the transducer is oscillatedabout its pivot point effecting a walking action to be imparted alongthe Wart me necessary rectilinear motion throughout the length of therib for the total rapid inspection of the workpiece. The transducer isadapted [52] US. Cl. 73/71.5 U, 73/678 S [51] Int. Cl. GOln 29/00 [58]Field oi Search 73/67.5, 67.6, 67.7, 67.8 S,

[56] References Cited to removably receive a dry adhesive couplant,which UMTED STATES PATENTS forms a driving mechanicalsjan'aafidaaoisticai cou- 3,541,840 11/1970 Phelan 73/715 U ple betweenthe piezo-electrical element of the trans- 3,628,374 12/1971 Laudien73/67.8 S ducer and the workpiece surface. 3,678,737 7/1972 Miller73/715 U Primary Examiner-Richard C. Queisser 13 Claims 12 DrawingFigures Assistant ExaminerArthur E. Korkosz Attorney, Agent, orFirm-Francis X. LoJacono, Sr.; Charles F. Dischler; L. Lee Humphries111111111111lllhhhllllhllhl PATENTED FEB SntEI 2 UF 6 um um] PATENTEU mm3 ii U PATENTEBFEB 51914 SHEET E OF 6 64 HOLE HOLE DISTAN ili l mo 2.]24

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RECTILINEAR ACOUSTICAL TRANSDUCER INSPECTION APPARATUS BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to anacoustical transducer used for ultrasonic inspection and moreparticularly to an ultrasonic inspection apparatus for inspecting structural stiffeners having rib Sections provided thereon.

2. Description of the Prior Art As is well known in the art variousproblems and difficulties have been encountered in providing aninspection tool having suitable means whereby a simple rapid inspectionof a workpiece can be performed to locate structural defects. There aremany varieties of inspection devices and methods widely practiced inmodern industry today. Since such testing is of particular importance inhigh-speed aircraft and space vehicles, wherein use of composite panels,either laminates or sandwich-type, is wide-spread and critical supportstructures are required to withstand an above average specificationprerequisite.

Heretofore it has been found most desirable to employ an ultrasonicprobe to discover disbonds in composite structures in a nondestructivemanner. Ultrasonic probes when employed with conventional electricalequipment produce a pulse of ultrasonic energy which is transmittedwithin the structure of the workpiece. The energizing signal isreflected in or attenuated upon coming into contact with anydiscontinuity within the workpiece, and this reflection or change inreceived signal amplitude is picked up by the probe and displayed bysome conventional means such as an oscilloscope. The acoustical pulse isusually produced by the application of the piezoelectric effect. Thepiezoelectric effect-is where certain materials ofa crystallinestructure (typically barrium titanate, lead zirconate, or leadmetaniobate) are caused to physically vibrate on application of avoltage gradient thereto producing a pulse of ultrasonic energy. Thecrystal structure of the probe physically deforms and produces amechanical pulse. The resultant acoustical pulse is transmitted into theworkpiece and any discontinuities within the workpiece are detected bythe reflection and/or attenuation of the returned signal.

The most common type of acoustical probe used for ultrasonic inspectionhas been particularly flat disc form. To effect the efficienttransmission of the electri cal pulse into the workpiece, an accuratesensing of the reaction, the flat disc probe typically requires the useof a liquid or a paste couplant which wets the workpiece surface andcouples the probe and the test article together acoustically. The probeis then moved translationally across the workpiece surface in a slidingrelationship therwith across the intervening film of couplant. Anydefects or disbonds located within the workpiece -are then detected byanalysis or comparison of each energizing pulse with its correspondingreflected pulse.

There are several disadvantages associated with the use of such probes.workpiece surfaces which are extremely rough or otherwise exhibit highfriction in respect to the probe, are difficult or impossible to inspectwith such a probe except by the complete immersion of both the probe andthe workpiece within the couplant material. Additional disadvantages ofthe wet coupling methods are that the couplants are messy, costly,involve risk of corrosion or contamination and usually leave residualtraces of the coupling medium.

Diffusion bonded structures are formed with thin wall stiffening membersranging in depth from one to several inches to form a component which isboth light in weight and strong. The stiffener sections are difficult toinspect. They are currently inspected by immersion techniques employingfocused probes. Multiple scans 1/32 inch increments) on each stiffenersection are re quired at each different bond line level. Side wallreflection from the water-metal interface make inspection difficult ifnot impossible in many cases. These reflections are caused by theimpedance mismatch at the water-metal interface. The noise level is sohigh in most cases that an adequate inspection cannot be made.

The innovative concept described herein will assure complete inspectionof most diffusion bonded or solid stiffener sections in the field with asingle rectilinear scan and without the use of water immersionapparatus.

SUMMARY OF THE INVENTION The present invention discloses an automaticrectilinear motivated ultrasonic probe for non-destructive testing toidentify internal defects within a rib section of a workpiece such asstructural stiffeners found in high speed aircraft and space vehicles.

The present invention comprises a carriage which is adapted to bemovably supported on an upstanding rib member of a workpiece that is tobe tested, said carriage includes a plurality of adjustable rollersoperably disposed therein for direct contact with the rib member,whereby the probe assembly in its entirety is transported along thelongitudinal rib member. Attached to the carriage is a probe mountingbracket having an extended arm portion adapted to movably support anultrasonic probe means in a position forward of the carriage memberwhereby oscillating and reciprocating action of the probe means impartslocomotion to the roller equipped carriage. The bracket member in oneembodiment is stationary relative to the carriage body while in analternative arrangement the bracket is attached to the carriage body insuch a manner as to provide a side to side rocking action.

However, the probe means in both embodiments is movably attached to thebracket and is oscillated forwardly and rearwardly in a linear directionalong the rib of the workpiece. Simultaneously it reciprocates in avertical direction to the rib of the workpiece. At each cycle the probemember itself comes first to an angular and then into direct planarcontact with the flat upper surface of the rib. This creates alocomotive action similar to walking. It, therefore, can be referred toas a walking probe. The probe means comprises a housing block adapted toreceive a piston assembly, which has disposed therein the ultrasoniccomponents necessary for recording the imperfections and flaws thatmight be found during testing of a workpiece.

In order to provide the proper walking action and contact along the ribportion of the workpiece there is provided a locomotive means whichincludes an elec. tric motor operatively connected to the pivotedhousing block by a cam assembly. As this cam is rotated by the motor-theblock will oscillate back and forth with the probe head being broughtinto full contact with the rib surface. To provide smooth movement ofthe probe and carriage, the housing block is permitted to slidably floatwithin a pivoted bracket in a vertical direction. This, together withthe spring loaded probe head allows the oscillation of the probe meansto walk along the rib rectilinearly with a positive sweeping overlappingsurveillance of every inch of the workpiece.

Various well known electronic components, such as Oscilloscopes,recording devices, etc., can be operably connected to the rectilinearlytransducer assembly for accurate readouts of each workpiece as they aretested.

OBJECTS AND ADVANTAGES OF THE INVENTION The present invention has for animportant object a provision whereby a workpiece having a rib member ormembers can be tested for imperfections, flaws, and other internaldefects without need of coupling liquids, paste, or submersion of thepart in a water tank.

It is another object of the present invention to provide a rectilinearacoustical transducer device having locomotive means together with a drycoupling means for the rapid inspection of welds, corrosion anddiffusion bonded structures by pulse echo techniques heretoforeunobtainable.

It is still another object of the present invention to provide a deviceof this character wherein the surface finishing is not a prerequisite tothe use of said inspection device.

It is a further object of the invention to provide a device of thischaracter that can be complemented by offthe-shelf electronic recordingapparatus.

It is still a further object of this invention to provide a device, ofthis character for inspecting rib sections on a workpiece havingelectrically driven locomotive means including a probe means having anoverlapping walking action along each rib section at an inspection rateof two to live feet per minute.

' Other characteristics, advantages and objects of this invention can bemore readily appreciated from the following description and appendedclaims. When taken in conjunction with the accompanying drawings, thisdescription forms a part of the specification wherein like referencesand characters designate corresponding parts in several views.

DESCRIPTION OF THE DRAWINGS Referring more particularly to theaccompanying drawings, which are for illustrative purposes only:

FIG. I is a side elevational view of the present inven tion mounted on arib section of a workpiece, the device being illustrated with a switchmeans and a recording apparatus connected thereto;

FIG. 2 is an enlarged top planned view of the device;

FIG. 3 is an enlarged side elevation of the invention with the probe infull contact with the rib member;

FIG. 4 is an enlarged end view of that shown in FIG.

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 2;

FIG. 6 is a sectional view taken somewhat along line 66 of FIG. 2;

FIG. 7 is an enlarged cross-sectional view of the ultrasonic probeassembly taken along line 7-7 of FIG. 2; v

FIG. 8 is a diagramatic illustration of the walking action which createsthe motivated transverse movement of the device along the rib section ofa workpiece;

FIG. 9 is a diagramatic illustration of the specific scanningcapabilities of a single walking contact over a defective area;

FIG. 10 is a diagram showing the comparison of the (db) response betweena walking motion and an up and down linear motion;

FIG. 11 is a diagram illustrating one means of recording the flaws anddefects within a structural workpiece;

FIG. 12 is a partial sectional view of an alternative embodiment of therectilinear transducer assembly.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly tothe drawings, there is shown in FIG. 1 an ultrasonic rectilinearacoustical transducer device generally indicated at l0 movably mountedon a rib stiffener section 12 of a structural workpiece I4. This deviceis operably connected by a switch means and a recording means indicatedgenerally by 16 and 18 respectively. These basic components provide anondestructive testing system capable of rapid inspection and detectionof imperfect welds, corrosion, flaws and various other defects inworkpiece, structures, particularly to those structures havingrectilinear stiffener rib sections as an integral part thereof.

In order to provide a nondestructive testing device to overcome the pastinspection problems, the above present invention comprises, a maincarriage indicated generally at 20, formed by two segments 22 and 23which are secured together to provide a means by which the components ofsaid device are supported for transverse linear movement. To accomplisha free rolling linear movement of the carriage, there is operablydisposed therein a roller guide means, said guide means includes aplurality of roller bearings 24 disposed hori zontally and alongitudinal channel 26 formed by the oppositely positioned inner wallsof segments 22 and 23; Roller bearings 24 are rotatably secured in placeby shaft pins 27 mounted within receding holes 28 and 29 of walls 22 and23 respectively. Channel 26 also defines a longitudinal opening alongthe entire length of the carriage for reception of rib stiffener 12 asillustrated in FIG. 5. It is essential that the carriage is centrallypositioned on the rib or structural stiffener 12 at all times. Sincealignment of the inspection tool 10 is critical, there is needed as partof the guide means a plurality of adjustable vertical roller bearings 30oppositely disposed to each other having adjustable means 32 whereby theroller bearings 30 can be adjusted along a horizontal plane relative tothe side faces 34 of the stiffener member 12. The stiffener members varyin widths from 3/16 of an inch to 2 inches and in depths of from 2 and1/2 to 4 inches with some workpieces weighing from 900 or 1,000 pounds.The adjustable means 32 of the rollers 30 can be accomplished in varioussuitable ways, but for illustrative purposes said means comprises athreaded lug 36 which is received in threaded holes 38 disposed in eachsegment 22 and 23 and centrally aligned with oppositely positionedcavities 40, said cavities being interposed in the lower portion of theinner wall of the segments 22 and 23. Received within each cavity 40 isa slidable bracket 42,

which is spring biased .by a leaf spring 43. Roller bearings areoperably coupled within the brackets 42 and are thereby brought intodirect vertical contact with faces 34 when lugs 36 are adjusted.

Secured to the carriage 20 along its upper flat surface is a supportbracket 44, to which the acoustical transducer probe assembly, generallyindicated at 45, is movably mounted. The movement of said probe assemblyis such that a back and forth oscillating action is imparted thereto bya locomotive means also attached in a suitable manner to the supportbracket 44. Said locomotive means, indicated at 46, imparts movement ofsaid probe which causes a linear walking action to occur to the probeassembly along said rib or stiffener. The details of which willhereinafter be described.

The acoustical probe assembly 45 comprises a pivotable frame 48,pivotably mounted to said support bracket 44 by pivot pin 49 (see FIG.6). Said frame 48 is provided with a backplate 50 which also is adaptedwith a central hole 51 for receiving said pivot pin 49. Extending fromeach outer corner of the backplate 50 is an arm 52, said arm beingarranged to form a compatible vertical set of upper and lower armswhereby a stationary rod 54 is fixed therebetween, as seen in FIGS. 4, 5and 7. The oscillating rocking actions as previously mentioned isdirectly imparted to the frame member by use of a drive end assembly 56which is an integral part of the locomotive means. Said locomotive meanscomprises an electric motor 58 interconnected to a gear assembly or box60 with an extended output shaft 62, said shaft being disposed within abore 64 located along the lower edge of bracket 44. There is mounted tothe free end of said shaft 62 a concentric wheel 56 having securedthereon an eccentric crank pin 66, said pin being received with bushing68 disposed in the lower portion of the ultrasonic acoustical probehousing block 70. The location of pivot pin 49 with relationship tocrank arm 66 creates an oscillating rectilinear motion of said probeassembly 45.

The probe housing block 70 is slidably mounted to the pivotable frame 48by means ofa plurality of stabilizing bushings 71 fixedly mounted withinoppositely arranged pairs of extended flanges 72 and 74. These flangesare an integral part of the probe piston block 70 and, therefore,provide a reciprocating substantially vertical sliding action withinframe 48 when said bushings are slidably supported on the verticalstationary rod 54. These can be seen in the section view of FIG. 7 aswell as FIGS. 4 and 5.

Thus, the various movements and actions are important to the properfunctioning of the probe and will hereinafter be described in moredetail.

Said probe housing block 70 is provided with a vertical bore 76 in whichthere is fixedly interposed therein an ultrasonic probe means, generallyindicated at 80, said means includes a cylindrical piston housing 82closed at its upper end by cap 84 and opened at its lower end by areduced diameter bore 85. Slidably received in an enlarged bore 86 ofthe piston housing 82 is piston member 87 defined by an enlarged head 88and a reduced diameter lower neck portion 89. The enlarged head havingsubstantially the same diameter as bore 86 and neck portion 89 havingsubstantially the same diameter of the reduced housing bore 84 (see FIG.7). Included in the piston head 88 is a small vertical bore 90 in whichis received electrical connecting means, generally indicated at 92.Adjacent the inner end of bore and communicating therewith is enlargedcavity 94 disposed in neck portion 89 whereby an acoustical probe head,indicated by numeral 96, is removably positioned therein. The probe head96 is adapted with a mating part of the electrical connecting means 90.However, it will be appreciated that various suitable electric connectormeans can be used to provide the required positive electrical connectionbetween the probe head and various power circuitries of any commercialavailable pulse echo, visually interpreted ultrasonic test equipment,and/or alarm recording systems for high speed inspection.

The probe head 96 is comprised ofa main solid cylinder like body 98having an outer diameter at least equal to the inside diameter of cavity94 in which said body is removably disposed. Extending below the body 98is an annular flange 99 providing an enlarged area which will bereferred to as foot 100. Said probe head 96 is formed of substantiallyresilient rubber like material and comprises a silicon material filledwith powdered metal to provide additional acoustical damping and anadequate impedance match with the loaded epoxy backing 104 on thepiezoelectric segment 102 which is fixedly disposed within the footportion 100. This combination provides for the proper flexible,mechanical support as well as an acoustical damping means for theextremely thin piezoelectric segment 102, to which a backing member 104is bonded, said backing member being formed of a substantially hardmaterial, it has been found that a combination of epoxy and tungstenpowder is quite satisfactory in providing acoustical match and dampingof the mechanical stress of piezoelectric segment 102. It, therefore,can be appreciated that member 104 in addition prevents fractures of thecrystal like segment 102 when in an operating mode. Both the crystalelement 102 and its associated backing member is allowed to freely movewithin probe head 96 since said material thereof is sufficientlyresilient to permit the piezoelectric element to depress slightly withinthe material as the probe is brought into press contact with the rib ofthe workpiece.

Due to the rectilinear walking action imparted to the probe means thereis also included an adjustable shock absorbing means indicated generallyat 106, which permits the probe head 96 along with the piston member 87to retract somewhat within the piston housing as the probe is pressedagainst the workpiece and then conversely as the probe is lifted awayfrom the workpiece spring 107 forces the probe head outwardly untilshoulder 108 of the piston 87 engages the inwardly extending annularshoulder 109 of the piston housing 82. Said spring 107 is disposed inbore 86 of the housing 82 having one end engaged against the pistonmember 87 and the opposite end thereof engaged under disc l0 which isslidably adjustable within bore 86 by means of a threaded adjusting bolt112, said bolt being threadably received in hole 114 centrally locatedin cap 84.

The piezoelectric sensing device is electrically connected by wires 116and 118 to connect plug means 92, more specifically the wires areattached to male plug 120, imbedded within body 98 and is received forelectrical connection with female plug 122, which in turn. is providedwith the necessary wire connection to an externally exposed adapter plug124. Said plug 124 can be of any suitable type that is adaptable for usewith the before mentioned commercial recording devices such as 18 seenin FIG. 1.

In order to provide the above described nondestructive testing devicewith a dry coupling means for use in place of various wetting agents,there is formed an acoustical dry coupling pad 126. This pad as used inconjunction with foot 100 and is defined as having a cup likeconfiguration of an elastomeric dry coupled material of which will bethe subject of its own application. However, this material provides athixotropic like surface action which results in a very low pressure drycoupled contact to the test article. Due to said material the need of avery smooth inspection surface is no longer required, therefore, rapidinspection of extremely rough surface structures without removing thecomponent from an aircraft is now possible. Thus, surface finishing isnot a prerequisite to inspection process with use of said thixotropiclike material of cap 12.6. The cap as used with the instant inventioncomprises a relatively flat surface circular face member 128 having anupright annular integral wall 130, said wall being formed with aninwardly projecting flange I32. Since said cap comprises a flexibleelastic material it then be comes very readily removable orinterchangeable depending on the composition to be tested.

WALKING AND SCANNING OPERATION The following is a description of thevarious elements previously described so that a better understanding ofthe rectilinear action can be understood.

Thus referring back to the drive pin assembly 56 which is driven by themotor 58 in either a clockwise or counterclockwise direction, and isillustrated by arrows 134 in FIG. 8 as a counterclockwise motion whereinthe counterclockwise action thereof produces a left to right linearmovement to said acoustical device indicated by arrows I35.

Drive pin 66 which is eccentrically secured to wheel 56 is suitablyjournalled in the probe housing 70 to cause said housing tosimultaneously oscillate back and forth and to reciprocate in an up anddown vertical action creating a compound movement of the probe assembly.This reciprocating action is in turn permitted by the sliding action ofhousing 70 within the frame 48, same frame being pivotally mounted tothe stationary bracket 44. The above walking action can be more readilyseen in FIG. 8 in which 44a represents 44, and 7011 represents housing70. Pivot pin 49 and frame 48a are shown stationary in both a verticaland horizontal plane, said frame only moving about pin 44a in a back andforth motion. However, it also can be seen that 70a oscillates with 44abut in addition reciprocates up and down therein due to 700 beingjournalled to pin 66 of wheel 56.

Position (a) illustrates the probe head assembly 96 separating from ribworkpiece 12. said assembly 96 is prevented from coasting forwardlyalong said rib in positions (1)) through (2) by built in function. Whensaid probe head assembly makes pressure contact with the workpiece forultrasonic scanning thereon through positions (f), (g) and (h), it walksforward along said rib one step. Position (1') begins another cycle. Thedis tance of forward travel between one contact point to the succeedingcontact point ofthe head 96 may be adjusted by the radial location ofdrive pin 66 in cam wheel 56 and for the location of pivot pin 49. Themcchanical arrangement ofembodiments l and 2 provide a step ofapproximately 3/8 of an inch with the linear travel of the device 10along the workpiece at a speed rate of two to five inches per minute. Itis important to note at this time that workpieces previously requiredtwelve hours to be inspected may now be automatically inspected in lessthan one hour and without the use of a liquid tank or contaminatingcouplant.

In order to more specifically illustrate the wide scanning range inwhich a flaw or imperfection is located. positions (f), (g) and (h) areshown enlarged in FIG. 9. Position (D of the probe head 96 begins asequential scanning action similar to the movement of a foot. that is,heel to toe motion wherein (/3 position represents the heel contact, (g)position the sole contact and (h) position represents the toe contact.During this progressive movement it can be seen that the scanning width(w) is such that if a flaw 250 is within the scanning area (w) and itwill remain within the scanning scope through the three positions (I),(g), and (h) as the probe rotates through center line aa. FIG. 9 isdrawn to illustrate the scanning effect only. The angles involved aresmall. The surface of the piezoelectric discovered with an elastic drycouple cap 126 (not shown in FIG. 9) this cap and the rubber footdistort with the angular movement providing a complete acoustical couplenot evident in the illustration. Therefore, each step is regulated toapproximately a 3/8 inch movement from each succeeding center line. Thusan overlapping acoustical beam scanning condition occurs therebyvirtually eliminating the possibility ofmissing a flaw or defect withinthe workpiece being inspected.

An additional important factor of the walking action of probe head 96should also be considered at this time, i.e., the dry couplant I26progressively forms a direct contact with the surface of the rib suchthat as it prr gressively rocks forwardly about the axis a-u all minuteair pockets are in essence squeezed out from under the face member 128whereby a dynamic coupling will exist between the workpiece surface andthe dry couplant material. To better illustrate the enhanced resultsfrom a positive walking action over that of an action in which the probeis brought into contact with the workpiece by a direct up and downvertical action, refer to FIG. 10. Hence, it can be readily seen thatthe walking motion indicated as dotted lines has a very high evenresponse compared to other linear motions. As a typical example of theend result that can be expected from said walking motion. refer to FIG.II which illustrates a scaled recording of a workpiece formed fromtitanium having a 3 H4 inch metal path using a 1/2 inch by l/2 inchtransducer. This workpiece was found to have three flaws in itsstructure, one being a 4/64 inch diameter hole and two 3/64 inchdiameter holes, one of which was' at a 2 degree angle as indicated onthe diagram. Each flaw is indicated several times on the recording (onepulse for each of 2 or 3 steps). The recording thus effectivelyillustrates the mechanical and acoustical beam scanning action obtainedwith the walking transducer assembly.

ALTERNATIVE EMBODIMENT Referring to the alternative embodiment, as shownin FIG. 12, there is included therein the major components ashereinbefore described in the preferred device. The major components arehereby indicated in FIG. 12, wherein the acoustical transducer device isgenerally indicated by reference character having a main carriage 142with oppositely disposed adjustable sidewalls 144 and 146, the carriageand walls being adapted with roller means for linear movement andsupport of device 140 when positioned on a workpiece to be inspected. Anadjustable means is provided for movement of the sidewalls, saidadjustable means comprises a bolt 147 centrally located between walls144 and 146, wherein the bolt is provided with right and left handthreads (not shown) similar to a turnbuckle, so that each sidewall iscapable of being adjusted inwardly and outwardly in unison. In addition,the walls are held in parallel slidable relationship through the use oftransverse guide pins 148, which are fixedly secured to carriage 144.Thus, said walls 144 and 146 are permitted to slide transversely alongthe pins 148 when said bolt 147 is rotated.

As in the first embodiment there is support bracket 150, said bracketbeing adapted to movably support the acoustical transducer assembly,generally indicated at 152, and fixedly support the locomotive meansindicated by reference character 154. Said transducer assembly comprisesthe basic elements of a pivotable frame 156 movably attached to saidsupport bracket 150 and having slidably mounted therein probe bodyhousing 158. A walking action is imparted to said as sembly 152 in asimilar manner as described in the original embodiment and as shown inFIG. 8. However, the differences between the first embodiment and thesecond embodiment is the additional element whereby the probe assembly152 can be adjustable to various angles relative to the linear travel ofthe device 140. That is, bracket 150 through an adjustment of an angleadjusting means 160 can be moved in an are about carriage 142. Saidangle adjusting means 160 includes a worm gear 162 and matching angularrack segment 163 which has the capability of being fixedly adjusted toprovide a predetermined angle of attack by the probe assembly 152. Hencethis will permit a larger area to be covered when the thickness of a ribsection is larger than the scanning area W. Under various scanningconditions that might be required the adjusting means is also capable ofbeing interconnected to the locomotive means, whereby the probe assemblywill oscillate together with bracket 150 transversely to that of thelongitudinal axis oftravel by the testing device 140. It will.therefore, simultaneously oscillate between and 2 as the walking actionalong the longitudinal curve occurs. The overall movement having anapproximate pivot action of 4, that is, two degrees to the left of theaxis and 2 to the right of the axis of travel. A 2 recording is shown inFIG. 11, wherein a 3/64 hole is recorded at a two degree angle settingof the probe.

Bracket 150 is secured to a pivotable platform 164 having depending endflanges 165 in which pivot pins 166 are mounted, said pins being adaptedto be received in opening 167 found in depending flanges 168 of asubstantially fixed slide plate 170 which is slidably affixed to saidcarriage 142. Thus, brackets 150 is oscillated by an operating meanscomprising a worm gear 162, which is secured to the pivotable platform164 and operably connected to rack 163 which is fixedly secured to slideplate 170. The slide plate 170 is permitted to be adjusted whenalignment of the probe head 172 is to be accurately located on the ribsurface.

The invention and its attendant advantages will be understood from theforegoing description and it will be apparent that various changes maybe made in the form, construction and arrangement of parts of theinvention without departing from the spirit and scope thereof orsacrificing its material advantages, the arrangement hereinbeforedescribed being merely by way of example, and I do not wish to berestricted to the specific forms shown or uses mentioned, except asdefined in the accompanying claims.

1. A rectilinear acoustical transducer inspection device fornon-destructive testing of a rib section on a workpiece, said devicecomprising:

a carriage;

a roller guide means operably supported by said carriage;

adjustable means for adjusting said roller guide means to provide directcontact with said rib section;

an acoustical transducer probe assembly operably attached to saidcarriage;

locomotive means operably connected to said probe assembly for impartinga linear walking action to said probe assembly in a step by step contactwith and along said rib section;

a support bracket mounted on said carriage whereby said probe assemblyis pivotably supported at the forward end thereof; and

means removably secured to said acoustical transducer probe assembly,and

wherein said acoustical transducer probe assembly comprises:

a pivotable frame, pivotably mounted to said support bracket;

a housing block slidably mounted to said pivotable frame and having avertical central bore disposed therethrough. said block being operablyconnected to said locomotive means whereby a walking action is impartedthereto; and

a probe means adjustably secured within said bore of said housing.

2. An inspection device as recited in claim 1 wherein said probe meanscomprises:

a piston housing;

a piston member slidably received within said piston housing; and

a probe head removably attached to said piston member.

3. An inspection device as recited in claim 2 wherein said probe headincludes:

a piezoelectric segment mountedtherein.

4. An inspection device as recited in claim 3 wherein said probe headcomprises:

a solid cylinder body having an enlarged annular foot, said body beingformed of substantially resilient material;

a powdered metal interspersed throughout said body;

and

a biasing means disposed within said piston housing and forcing saidprobe means outwardly therefrom.

5. An inspection device as recited in claim 4 wherein said piezoelectricsegment includes:

a backing member secured to one side of said piezoelectric segmentwherein both are fixedly disposed within said foot.

6. An inspection device as recited in claim 5 wherein said backingcomprises:

a substantially hard epoxy material; and

a powdered metal interspersed therethrough.

7. An inspection device as recited in claim 6 wherein said powderedmetal comprises:

a tungsten powder. 8. An inspection device as recited in claim 7 whereinsaid dry coupling means comprises:

an elastomeric flexible cap wherein said foot of said probe head iscovered thereby providing a low pressure contact between said probe andsaid workpiece. 9. An inspection device as recited in claim 8 whereinsaid locomotive means comprises:

an electric motor; a gear assembly interconnected to said motor; aconcentric wheel operably driven by said gear assembly; and a crank pineccentricly mounted to said concentric wheel, said pin being operablyreceived in said housing block. 10. An inspection device as recited inclaim 3 wherein said device includes:

a recording means operably connected to said device and remotelypositioned therefrom.

11. An inspection device as recited in claim 10 including:

means for electrically interconnecting said probe head to said recordingmeans.

12. An inspection device as recited in claim 10 wherein the direction oflinear movement of said device is controlled by a switch means operablyconnected thereto.

13. An inspection device as recited in claim 3 wherein said deviceincludes:

a pivotable platform movably mounted to said carriage and having saidbracket supportingly fixed thereto whereby said acoustical transducerprobe is oscillated transversely to the rib section of the workpiece;and

an operating means interconnecting said locomotive means with saidpivotable platform.

1. A rectilinear acoustical transducer inspection device fornon-destructive testing of a rib section on a workpiece, said devicecomprising: a carriage; a roller guide means operably supported by saidcarriage; adjustable means for adjusting said roller guide means toprovide direct contact with said rib section; an acoustical transducerprobe assembly operably attached to said carriage; locomotive meansoperably connected to said probe assembly for imparting a linear walkingaction to said probe assembly in a step by step contact with and alongsaid rib section; a support bracket mounted on said carriage wherebysaid probe assembly is pivotably supported at the forward end thereof;and means removably secured to said acoustical transducer probeassembly, and wherein said acoustical transducer probe assemblycomprises: a pivotable frame, pivotably mounted to said support bracket;a housing block slidably mounted to said pivotable frame and having avertical central bore disposed therethrough, said block being operablyconnected to said locomotive means whereby a walking action is impartedthereto; and a probe means adjustably secured within said bore of saidhousing.
 2. An inspection device as recited in claim 1 wherein saidprobe means comprises: a piston housing; a piston member slidablyreceived within said piston housing; and a probe head removably attachedto said piston member.
 3. An inspection device as recited in claim 2wherein said probe head includes: a piezoelectric segment mountedtherein.
 4. An inspection device as recited in claim 3 wherein saidprobe head comprises: a solid cylinder body having an enlarged annularfoot, said body being formed of substantially resilient material; apowdered metal interspersed throughout said body; and a biasing meansdisposed within said piston housing and forcing said probe meansoutwardly therefrom.
 5. An inspection device as recited in claim 4wherein said piezoelectric segment includes: a backing member secured toone side of said piezoelectric segment wherein both are fixedly disposedwithin said foot.
 6. An inspection device as recited in claim 5 whereinsaid backing comprises: a substantially hard epoxy material; and apowdered metal interspersed therethrough.
 7. An inspection device asrecited in claim 6 wherein said powdered metal comprises: a tungstenpowder.
 8. An inspection device as recited in claim 7 wherein said drycoupling means comprises: an elastomeric flexible cap wherein said footof said probe head is covered thereby providing a low pressure contactbetween said probe and said workpiece.
 9. An inspection device asrecited in claim 8 wherein said locomotive means comprises: an electricmotor; a gear assembly interconnected to said motor; a concentric wheeloperably driven by said gear assembly; and a crank pin eccentriclymounted to said concentric wheel, said pin being operably received insaid housing block.
 10. An inspection device as recited in claim 3wherein said device includes: a recording means operably connected tosaid device and remotely positioned thErefrom.
 11. An inspection deviceas recited in claim 10 including: means for electrically interconnectingsaid probe head to said recording means.
 12. An inspection device asrecited in claim 10 wherein the direction of linear movement of saiddevice is controlled by a switch means operably connected thereto. 13.An inspection device as recited in claim 3 wherein said device includes:a pivotable platform movably mounted to said carriage and having saidbracket supportingly fixed thereto whereby said acoustical transducerprobe is oscillated transversely to the rib section of the workpiece;and an operating means interconnecting said locomotive means with saidpivotable platform.